-LRB- CNN -RRB- -- A North Korean soldier on guard duty at the border dividing the two Koreas defected , telling authorities who received him in the South that he killed his superiors before fleeing across the Military Demarcation Line .

South Korean soldiers at their guard posts reported hearing gunfire before he crossed into the South shortly after noon local time , according to a news release from South Korea 's Joint Chiefs of Staff .

Soldiers in the South took the defector in on their side of the border and brought him to a safe place for questioning then tightened security in the area .

The North Korean said that `` while he was on guard duty , he killed his platoon and squad leaders and defected thereafter , '' the JCS said .

Defections over land through the heavily armed and fortified Demilitarized Zone -LRB- DMZ -RRB- are rare , as most fleeing the communist North prefer the greater odds of success of crossing by sea .

`` The last North Korean soldier who defected -LRB- over land -RRB- was in March 2010 , '' said a spokesman from the defense ministry in Seoul .

But with his comrades dead and no longer capable of hindering him , it was easy for the soldier to flee south .

`` The distance between the North Korean guard post and the South Korean guard post is 500 meters , '' the official said , who asked not to be named , because he is not authorized to speak with the media .

More than 24,000 refugees have entered the South from the North since the country 's division , according to the Ministry of Unification in Seoul , over two-thirds of them women .

The annual number of refugees has climbed steadily from less than 100 in the 1990s to more than 2,000 per year since 2006 .

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South Korean soldiers hear gunfire before the defector crosses

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The North Korean says he killed his platoon and squad leaders

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Defections over land via the heavily armed DMZ are rare

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The number of refugees fleeing per year has climbed dramatically over the years